Hello guys…

I hope you are doing well in your study. I generally write
articles on Automobile, Production etc. But now we are going to start to provide
best quality articles on strength of material which is an interesting subject
and also a very important as exam point of view. It is our first article in
this segment. I hope you like it and if you want to learn this
subject I suggest you to subscribe our website.

This is our first article and most of you know that SOM is
totally depended on stress and strain concept. If you are able to understand these two word
completely, you will never find any difficulty in this subject.

Now stop rounding, let’s start the discussion.

##
Stress and Strain??

### What is stress?

Let’s learn with an example. Take a rubber band and start to
pull it. Now remove the load and observe its behavior. The rubber band gets its
initial dimensions completely. Now take a wire or rod of steel and start to pull
it. What will happen? The steel wire is not permitting the deformation on
manual loading. Ok let’s pull it through an external loading and observe it on
microscopic level. If you observe it consciously, you will find that it also
deform and gets back its original position after removing the load.

We can also observe that if we increase the loading
continuously, it will break the wire or after removing the load the wire does
not get its original dimensions.

In above example, we have observed that the steel wire need
more load to deform compare to rubber wire and also rubber wire deform more. Both
of steel and rubber wire gain their initial dimensions after removing the load. Why
it so?

After performing this experiment, we can conclude that there
is a reinstating force in any material which tends to resist deformation. The
rubber wire have small reinstating force so it deform easily while the steel
wire had high reinstating force which need more load to deform it. This resisting
force per unit area is called

**STRESS**. In an equilibrium condition, this resisting force is equal to the applied load.
According to the definition resisting force per unit area induced in the body during external loading is called stress. We have discussed
that the resisting force induce in the body is equal to the applied force so mathematically
stress is ratio of the applied load to the cross section area of the body. It
is represent by the symbol

**σ**.
According to the loading stress can be divided into two
categories.

The first one is normal stress in which the load is either
compressive or tensile. Both of these loads try to deform the initial dimension
of the body.

The other one is shear stress in which two equal and
opposite loads are applied to the parallel faces of the body which try to
deform its dimension.

I think at this point you have confusion between elasticity
and stress and how both are differ. Don’t be confuse, the elasticity is the
property of any material due to witch it get its initial dimension after
removing loading while the stress is induce in the body due to loading which tends to resist
deformation. The stress is also depends on the shape of body while the
elasticity is depend on material.

Now we start to discuss about strain:

### What is stain?

The strain is just a measurement of deformation induce by
the application of stress. According to the definition the ratio of change in
dimension to its original dimension is called strain.

Let’s remember the previous examples. When we stretch the
wire, the initial length of wire is

**L**and after stretching the length of wire become**L +**∆L. The ratio of ∆L to**L**is called**STRAIN**. It is denoted by**ɛ**.
Now I think one confusion striking your mind that why we need
this type of measurement or why the researchers describe this quantity. The
answer is quite simple because the stress is directly proportional to strain.
So we have to measure strain to describe the relationship between stress and
stress. These both term relationship describe the safe loading, and deformation
phenomena of any body.

Same as stress, strain can also divided into compressive
strain, tensile strain and shear strain. There are two more different types of
strain called lateral strain and longitudinal strain which we will discuss in
next article.

Today we have learnt about stress and strain. I hope you
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